This invention relates to a composition for the removal of a wide variety of paint films from solid substrates.
Compositions for stripping paint films from solid substrates are well known and have been in the marketplace for many years. Paint strippers are basically of two fundamental types; the so-called hot strippers that function at elevated temperatures and the so-called cold strippers that function without the need for added heat. Examples of so-called hot stripper compositions are given in U.S. Pat. No. 3,576,673 issued Apr. 27, 1971 to Harry R. Charles et al. These compositions are basically highly alkaline aqueous compositions which are used at temperatures around 180.degree. F. With the advent of escalating energy costs, the hot strippers have become less favored than the cold strippers. Additionally, hot paint strippers have a number of problems associated with their use, such as rapid bath depletion; the need for constant additions of replenisher; lack of a simple replenisher control method; metal discoloration; odor and fume problems; and safety problems associated with the use of hot alkali solutions.
Cold paint strippers, which are generally nonaqueous compositions formulated with chlorinated hydrocarbons, usually remove paint more quickly than the hot stripper compositions. However, cold paint strippers have their own problems. For example, they cannot be diluted with water; they have extremely high charge-up costs; they have a high evaporation rate even at room temperature; and they also have odor and irritation problems.
Examples of compositions for cold stripping are given in U.S. Pat. No. 3,335,087 issued Aug. 8, 1967 to James Joseph Keers, Jr. and U.S. Pat. No. 3,950,185 issued Apr. 13, 1976 to Mitsuo Toyama et al. The Keers patent discloses compositions containing hydrofluoric acid, hydroxy aromatic compounds and chlorine substituted hydrocarbons. The Toyama et al patent related to compositions containing halogenated hydrocarbon solvents and a pressure sensitive adhesive component. Use of compositions containing hydrofluoric acid as disclosed in the Keers patent presents health and safety problems which limit their use. Compositions such as those disclosed in the Toyama et al patent have the disadvantage of requiring a paper or cloth to be placed on the film-removing composition and then peeling off the paper or cloth, taking with it the paint film. As well as being time and material intensive, such a procedure is, of course, impractical for articles with complex surfaces.
Additionally, cold paint strippers in commercial use usually contain large quantities, e.g. 80-90%, of methylene chloride as the chlorinated hydrocarbon. Such compositions, while effective, tend to be expensive due both to the initial cost of the methylene chloride and to the fact that even under relatively cool conditions methylene chloride has a high vapor pressure and, therefore, a high evaporation rate.